Notes on the satellites of Saturn

Abstract

THE object glass of the telescope used in the observations which follow is of twelve and one-third inches diameter. Its deo ni tion is good. The telescope is used in such observations as its very imperfect mechanism will allow; the;;e are observations of the conjunctions of the satellites with the edge of Saturn's ring, of size and color, and of differences of right ascension. The last are made b.y connecting with the chronograph, and recording the time of passage of the satellites over a fixed wire. In the course of these observations such different relati ve magnitudes have been given to the small satellites, on different evenings, as to lead to the suspicion that some of them are variable. 'rhe sparkle of Tethys and the grayish blue color of Hhea make it seem unlikely that sUlall stars can have been taken for these two satellites; 'in the case of Encelad us and Dione m istakes are more easily made; but the rapid motion of Enceladus soon establishes its identity. The most noticeable changes are in Rhea. In 1877, Hhea is recorded as small on Nov. 30th; as dull on Dec. 3d; as blurry and large, Dee. 14th; and as ruddy, Dec. 18th. In 1878 Rhea is recorded as faint Oct. 3d and Oct. 16th; as bright on Oct. 25th, and on Dec. 3d it is called nearly as bright as 'ritan.